The present invention relates to valves of the type employing a pivoted butterfly type movable valve member. Valves of this type are typically employed in automotive applications for controlling flow of engine coolant to and from the passenger compartment heat exchanger or heater core. In such automotive heater core valve applications, it is known to provide a metal butterfly plate spot welded to a pivot shaft rotatably mounted through the walls of the valve housing for connection to an external actuator. Metal plate butterfly valves employed for automotive heater core applications typically are fabricated by inserting the valve plate in a mold and molding an elastomeric bead-rim thereabout for facilitating sealing of the periphery of the metal plate about the wall of the flow passage in the valve housing which is typically formed of die-cast metal or molded thermoplastic material. This method of construction by molding an elastomeric rim on a metal plate and then spot welding the plate to the actuator shaft in the valve housing has proven to be quite costly in the high volume mass production required for automotive heater valve applications.
Furthermore, the aforesaid butterfly valve construction having a metal butterfly spot welded to the actuator shaft has been prone to breakage of the spot welds in service where the actuator shaft experiences overtravel, after the butterfly valve has closed against the wall of the flow passage in the valve, particularly in servomotor powered valve applications. Thus it has been desired to find a way or means of constructing a butterfly valve which is capable of being mass produced in high volume, such as for automotive heater applications, at a low manufacturing cost, and which provides reliable service and will readily absorb some degree of actuator overtravel in service without breakage.